The present invention relates to a target for use with a laser generating device and, more particularly, to a target for use with a laser generating device which generates a reference laser beam of light for establishing a reference plane or reference line for use in construction.
Laser beam generating devices have long been used in construction applications to create a reference for leveling, aligning, setting a grade or surveying. For example, rotating laser beam projecting devices have been used to establish a reference plane for laying foundations, setting frame work, or grading. Stationary laser beams, on the other hand, have been used to establish reference lines of light. Reference lines of light are used, for example, for surveying, aligning pipes, or determining the proper height for components, such as duct work, ceiling frame work, or the like.
It is also known to use a target in combination with laser generating devices in which the laser beam is directed onto the target in order to measure height, to set a height or to position an object to which the target is mounted, or to position a laser to a desired orientation. Targets typically have some indicia, for example concentric circles, vertical lines, horizontally spaced lines or the like. For example, when aligning a pipe, a stationary laser beam generating device is positioned on one end of the pipe and a target is placed on the other end of the pipe so that when the light beam from the laser generating device intercepts the target at a desired position on the target, the pipe is properly positioned or aligned. These targets can be, therefore, used as a reference for setting and aligning the pipe at a desired grade and azimuth and, further, for establishing a reference for excavation of the trench and grading of the sub-bedding beneath the piping. However, in order to determine whether the laser beam is properly positioned on the target, the operator must detect where the laser beam hits the targetxe2x80x94for example, whether the laser beam hits the center or bulls-eye of the target. Since piping is often laid in a trench beneath the ground surface, it is often hard for the operator of the laser system to detect where the beam passes through the target relative to the indicia on the target.
In an effort to enhance the visibility of the reference beam, lasers using different portions of the optical spectrum have been developed, for example, lasers generating laser beams in the green portion of the optical spectrum. In addition, targets have been developed that employ a refractive surface in order to bend the light from the reference beam up to the detector, such as the operator, to orient the laser beam so that it is more visible. A common refractive surface that is employed is a spherical shape either with a positive or negative focus. The shape is either molded or bead blasted onto the optical material forming the target. Simple refractive surfaces exhibit a dipole like radiation pattern illustrated in FIG. 2. This dipole-like-radiation pattern, however, creates a low brightness function for the eye due to the rather large solid angle over which the refracted light transmits. For example, most optical plastics have a total internal reflection of 1.47 and, therefore, such surfaces are limited to refracted angles of less than 55xc2x0 due to the law of total internal reflection. Complex refractive surfaces, such as parabolic, cylindrical, or toric, have been used to bend more light toward the detector by adding an off-axis shift to the dipole pattern. However, these complex refractive surfaces still have a basic restriction due to the law of total internal reflection. In addition, referring to FIG. 3, a complex refractive surface refracts light over a large solid angle. While the brightness function may posses a slight improvement due to the offset axis shift, these complex refractive surfaces are more expensive to manufacture due to molding and cutting.
Consequently, there is a need for a target which can bend the light from a laser generating device to produce a bright or intense light that forms a high angle with respect to the optical axis of the target so that the position of the laser beam on the target is more easily detected by a detector, such as a human eye.
According to the present invention, a target for a laser beam generating device exhibits high intensity or brightness while bending the light at a high angle with respect to the optical axis of the target so that the position of the laser beam as it passes through the target is more easily detected by a detector, such as a human eye.
In one form the invention, a laser target for use with a laser generating unit includes a target body which is formed from an optical material and has an optical axis. The target body is adapted to diffract a reference laser beam of light which is directed to the target body along the optical axis to provide a diffracted beam which is more visible to a human eye.
In one aspect, the body diffracts the laser beam in a multi-lobe pattern, in which at least one of the lobes is angled greater than 40xc2x0 from the optical axis of the target body, more preferably, greater than 50xc2x0 from the optical axis and, most preferably, greater than 60xc2x0. For example, the multi-lobe pattern may include more than three lobes.
In further aspects, the optical material is adapted to diffract the laser beam. For example, the optical material may include a plurality of diffractive bodies which diffract the laser beam. In preferred form, the diffractive bodies are dimensioned on the same order of magnitude as the wave length of the light generated by the laser generating unit. Preferably, the diffractive bodies comprise generally spherical particles. Suitable diffractive bodies include, for example, macromolecules, and have dimensions in a range of approximately 0.1 microns to 5.0 microns and, more preferably, in a range of approximately 0.1 microns to 2.0 microns.
In another form of the invention, a laser target for use with a laser generating unit includes a target body formed from an optical material with the target body having an optical axis. The target body includes a plurality of diffractive bodies that diffract a reference laser beam of light which is directed to the target along the optical axis to produce at least one diffracted beam at an angle in a range of about 40xc2x0 to 90xc2x0 from the optical axis of the target body.
In one aspect, the body includes a carrier which includes the diffractive bodies. For example, the carrier may comprise a tape with the diffractive bodies, for example, etched onto the tape or provided on the tape in the form of a hologram.
In another aspect, the target body comprises an optical material having a colloidal suspension for diffracting the reference laser beam in a multi-lobe pattern. For example, the optical material may comprise a polymer.
According to yet another form of the invention, a laser target for use with a laser beam generating device is formed by molding a target body and adapting the body to diffract a reference laser beam of light directed toward the target body along the target body""s optical axis.
In one aspect, the target body is molded from a polymer with diffractive bodies. For example, the diffractive bodies may be formed by forming a colloidal suspension in the polymer. In another aspect, a carrier having a plurality of diffractive bodies is provided and is applied to the target body. For example, the carrier may be affixed to the target body by an adhesive. In another aspect, submicron dots may be formed on the carrier to provide the diffractive bodies. For example, the submicron dots may be formed by depositing the submicron dots on the carrier. Alternately, the diffractive bodies may be formed by photo-etching the carrier with the submicron dots.
These and other objects, advantages, purposes, and features of the invention will become more apparent from the study of the following description taken in conjunction with the drawings.